High-dose phosphorus-ion (P+) implantation into off-axis 4H-SiC (0001) and high-temperature annealing with a graphite cap have been investigated. The authors successfully developed a more convenient technique to suppress surface roughening by using a graphite cap made from a standard photo-resist. The implant-dose dependence of sheet resistance for P+-implanted SiC was also investigated. The sheet resistance (resistivity) takes a minimum value of 45 Omega/sq. (0.9 mOmegacm) at an implant dose of 6.0 x 10(16) cm(-2). This resistivity is the lowest ever reported. There is no significant difference between graphite-cap-annealed and bare-annealed SiC in terms of sheet resistance.